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Cover crops reduce water drainage in temperate climate. A Meta-Analysis. PS-5.1-01

Meyer Nicolas, Constantin Julie, Bergez Jacques-Eric, Justes Eric. 2018. Cover crops reduce water drainage in temperate climate. A Meta-Analysis. PS-5.1-01. In : Book of abstracts of the XV European Society for Agronomy Congress : "Innovative cropping and farming systems for high quality food production systems". Agroscope. Genève : Agroscope, Résumé, 35. European Society for Agronomy Congress (ESA 2018). 15, Genève, Suisse, 27 Août 2018/31 Août 2018.

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Résumé : Cover crops are grown during fallow period between two main cash crops and biomass is returned to the soil at their destruction. They provide many ecosystem services such as nitrate leaching reduction or green manure effect. However, the impact of these multiservices cover crops on water balance is poorly studied. Some papers reported an increased evapotranspiration due to an increase of plant transpiration that could decrease water drainage. Nevertheless, there is no consensus on the intensity of their impact on water budget. Less drainage could reduce groundwater water recharge, which can be a crucial issue, particularly in dry regions and in a climate change context with more frequent drought. Since the impact of cover crops on water cycle and drainage can be a serious disservice, particularly if generalized over large spatial area, our objective was to study the effect of cover crops on drainage through a meta-analysis. We carried out a meta-analysis to compare drainage under cover crops versus bare soil in temperate climates. From an initial database of more than 280 references, we selected 34 studies having available data on drainage, including a comparison between cover crops and bare soil at field scale from both experiments and modelling study. Despite high variability of climate, soil, and cover crop management, cover crops reduced water drainage in more than 90% of the 34 studies. The mean effect size reported a water drainage reduction of 31 mm with a confidence interval at 95% between 41 mm and 22 mm. This reduction indicates that evapotranspiration was higher with cover crops compared to a bare soil, the reduction of soil evaporation by the plant cover being lower than the cover crop transpiration. A slight higher reduction of drainage was obtained for modeling results than for field measurements, as well as for cover crops sown during summer than during autumn and on medium soil texture than on loamy or clay soils. However, these trends were not significantly different due to the low number of studies for each situation. More experiments with close monitoring throughout the fallow period are needed to determinate the water flux modification explaining the drainage reduction by cover crops. Modelling could also be a complementary tool for analyzing and quantifying the water dynamics on a wide range of pedoclimatic conditions, as a first work for proposing optimal managements of cover crops avoiding a too strong reduction of drainage in dry regions where groundwater recharge is a crucial issue.

Auteurs et affiliations

  • Meyer Nicolas, INRA (FRA)
  • Constantin Julie, INRA (FRA)
  • Bergez Jacques-Eric, INRA (FRA)
  • Justes Eric, CIRAD-PERSYST-UMR SYSTEM (FRA) ORCID: 0000-0001-7390-7058

Source : Cirad-Agritrop (https://agritrop.cirad.fr/588916/)

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